glXMakeCurrent does two things: It makes ctx the
current GLX rendering context of the calling thread, replacing the previously
current context if there was one, and it attaches ctx to a GLX drawable,
either a window or a GLX pixmap. As a result of these two actions, subsequent
GL rendering calls use rendering context ctx to modify GLX drawable drawable.
Because glXMakeCurrent always replaces the current rendering context with
ctx, there can be only one current context per thread.

Pending commands
to the previous context, if any, are flushed before it is released.

The
first time ctx is made current to any thread, its viewport is set to the
full size of drawable. Subsequent calls by any thread to glXMakeCurrent
with ctx have no effect on its viewport.

To release the current context
without assigning a new one, call glXMakeCurrent with drawable set None
and ctx set to NULL

glXMakeCurrent returns True if it is successful, False
otherwise. If False is returned, the previously current rendering context
and drawable (if any) remain unchanged.

A process is a single-execution
environment, implemented in a single address space, consisting of one or
more threads.

A thread is one of a set of subprocesses that share a single
address space, but maintain separate program counters, stack spaces, and
other related global data. A thread that is the only member of its subprocess
group is equivalent to a process.